Phenols witch hazel

FIGURE 11.24 Leaching (a) Standard pieces of different trees leach out different amounts of phenolics and other compounds. During 24 hours, red maple and witch hazel (left) stain water a darker brown than willow and quaking aspen (right), (b) and (c) Beavers leave pieces of branches in the water for 1-3 days with some or all bark intact before eating the bark. This presumably leaches out water-soluble plant secondary compounds. 

This part deals with the possible effects of leaching out plant secondary compounds from usually less preferred food. Offer beavers sticks 30-cm long (1-cm diameter) of trees known to contain high levels of phenolics such as witch hazel (Hamamelis virginiand) or red maple (Acer rubrum). Half of the sticks are untreated, and the other half has been soaked in water for 2-3 days. As control, offer a preferred food such as untreated aspen. 

The biological functions of such plant secondary metabolites (PSMs) have been debated for a long time. They often have antimicrobial functions, but also serve as repellents and feeding inhibitors against herbivorous insects and vertebrates, notably birds and mammals. Animals have evolved many mechanisms to cope with phenolics in their diet. These start with food processing. For instance, beavers consume experimental sticks of the phenolics-rich witch hazel only after leaving them in the water for 2-3 days, apparently to leach out unpalatable compounds (Miiller-Schwarze et al. 2001). Many birds and mammals eat clay to adsorb phenolics so they never will be absorbed in the intestines. If they are taken up in the blood stream, such PSMs will eventually be rendered harmless by oxidation and other processes, followed by conjugation, in the liver. They then will be excreted in the urine. 

Gallic acid (also called 3,4,5-trihydroxybenzoic acid) (Figure 2.17) is a natural plant phenol. It is an organic acid found in walnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. Gallic acid has been found to... 

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See also in sourсe #XX -- [ ]

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